Myelin basic protein (MBP)-specific T-cells may play an important role in the pathogenesis of multiple sclerosis (MS). Vaccination with irradiated autologous MBP-reactive T-cells (T-cell vaccination) induces cytolytic anti-clonotypic T-cells that specifically recognize and lyse the immunizing T-cells, resulting in selective depletion of circulating MBP-reactive T-cells in patients with MS. The current application is designed to elucidate molecular mechanisms underlying T-cell vaccination and clonotypic regulation of MBP-reactive T-cells in MS. There are three specific aims: (1) to generate and characterize anti-clonotypic T-cells that are induced by T-cell vaccination and specifically regulate MBP reactive T-cells in MS. Selection of DR2 restricted 84-102 specific T-cells for vaccination is based on potential structural similarities in their T-cell receptors (TCR) and their representative value for a large proportion of the MS population, (2) to locate and identify the target TCR regions and common sequence motifs recognized by anti-clonotypic T-cells and (3) to design MHC class I bound TCR peptides and evaluate their specificities and efficiency in eliciting cytolytic anti-clonotypic T-cells in DR2 MS patients. The purpose of this study is to improve and simplify the current T-cell vaccination protocol using a peptide-based vaccination approach. A large panel of cytolytic anti-clonotypic T-cell lines will be generated from MS patients vaccinated with autologous DR2-restricted T-cell clones specific for the immunodominant MBP peptide (84-102). The resulting anti-clonotypic T-cell lines will be characterized for their recognition pattern(s) towards the immunizing T-cell clones. V or V gene segments of the immunizing T-cell clones will be introduced genetically into autologous B-cells with truncation/deletion to identify and narrow down the TCR region/sequences capable of eliciting the anti-clonotypic T-cell responses. Specific attention will be given to identifying common sequence motifs within the target region(s) in the context of appropriate MHC class I molecule(s). Based on the obtained sequences data, a panel of short peptides will be designed and evaluated for their specificity and efficiency in eliciting cytolytic anti-clonotypic T-cell responses in DR2 MS patients. A MHC class I bound peptide(s) designed to incorporate common sequence motifs characteristic of DR2-restricted 84-102 specific T-cells will have great potential in the treatment of a large proportion of patients with MS.